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Is Carb Adjustable???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Canuck, Jun 2, 2000.

  1. Canuck

    Canuck 1/2 ton status

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    I have an 86' K5 Silverado (totally stock/original). The truck is running extremely rich and I'm sure we all know Blazers are not the best on gas normally. You can litterally smell the unburnt gas exiting the exhaust. My buddy looked at the carb (since I am not an expert) and told me that the carb is non adjustable as far as the air/fuel mixture is concerned. Was he just lazy or is it not adjustable??? Any input would be appreciated.

    Canuck
     
  2. 83K5

    83K5 Registered Member

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    If it has a carb there is tool that will drill out the plugs covering the mixture screws . You can get one from JC Whitney or a Napa store .
     
  3. Eagle86K5

    Eagle86K5 1/2 ton status

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    The fuel /air adjusment needles are set from the factory and plugged. Take the carb off and you can drill them out. Good time to rebuild while you have it off...

    <font color=green>[​IMG]Eagle86K5[​IMG]<font color=red>
    Masonry...It's a Good Thing
    2B1ASK1
     
  4. Blazer1970

    Blazer1970 1/2 ton status

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    The idle adjustment is factory set, and therefore, it is most likely set right. You need to rebuild your carb, as something else is wrong with it. You do not want to try to compensate by adjusting the idle mixture.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    If you look at your carb with the air cleaner off you will notice a wire on the top of the carb. The 86 had electronic mixture control. Make sure that wire has 12v. If it has 12v check to see that the wire running to the sender on the watter neck (follw the wires) shows ground when the engine is warm. Check it with the wire disconnected. If it shows ground then you may have a bad mixture solinoide. The rebuilt carbs for them are EXPENSIVE!!!!!!!!!!! Personaly if it were me I would pull the electric choke (speaking of witch make sure the choke is opening fully when hot again check for 12v if it isn't if it has power then you got a bad element ...$27 bucks autozone) and see if you can swap it for a carb for an78-79. It will have all the correct hook ups for the emmisions except it has the mechanical mix. It is also about a $100 bucks cheaper. compair the carbs before you leave an make sure it has the same vac connections and as long as it does it will work fine and bolt right up.

    Diging it in the dirt with my K5's
    Grim-Reaper
     
  6. Zack

    Zack 1/2 ton status

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  7. Canuck

    Canuck 1/2 ton status

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    WOW; That sounds like some excellent info. I'll do some checking. What do you think of a Holly carb replacement? I have had some good luck with them on my other vehicles.

    Canuck
     
  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    ZZZZZZZZiiiip Flame suit on. Holly's don't even make good boat anchors. (my oppinion and I will stick with it)
    Personaly I would stick with the Quad. While it takes a while to get a Quad set up, once set up they will be trouble free for a LONG time (hay you went 14 years on the first one). The Holly's are very prone to off camber stall problems and just plain bite off road because of the float design. Now the early Quads do have some isues of stalling when you get the nose WAY up but after 77 that was taken care of. Thats why I recomend the 79 or so model. They seem to be the best all around. They will run the full gamit of emmisions but they don't have that electric mix control. They can easily be converted to electric choke. Now one other thing to check. Some of the electric mix Quads had a O2 sensor. If your truck has the O2 it may be whats wrong. They are about $35 bucks.
    Also the 2 screws at the base only control idle mixture. they will help lean out at low RPM (till about 1700) but the only other way to lean the truck out is to change the metering rods and primary jets. Since this carb still has the plugs It sounds original to the truck so that should not be the problem. Now here is a good hint....you carb is already set fairly well for the engine. Take the metering rods and jets out if your going to use it as a core on a rebuild. They will never know they are missing when you turn it in as a core. If your still running rich with the new one you can put the other rods and jets in and it should get you on the money. Also your truck has a butt load of vac lines...check them and replace any that are hard or cracked. In fact do that first before you do anything else.

    Diging it in the dirt with my K5's
    Grim-Reaper
     

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